Field of the Invention
The presently disclosed subject matter relates to a laminate film, a backlight unit, a liquid crystal display device and a method for producing a laminate film, particularly relates to a laminate film that enables to enhance luminance, and a method for producing this laminate film. Furthermore, the presently disclosed subject matter also relates to a backlight unit including this laminate film, and a liquid crystal display device including this backlight unit.
Description of the Related Art
Applications of a flat panel display such as a liquid crystal display device (LCD: liquid crystal display) (hereinafter, also referred to as “LCD”) as a low power consumption and space-saving image display device are widespread year by year. The liquid crystal display device is configured from at least a backlight and a liquid crystal cell, and usually further includes members such as a polarization plate facing the backlight and a polarization plate facing the viewer.
In the flat panel display market, an enhancement in color reproducibility progresses as an improvement in LCD performance. With respect to this point, a quantum dot (also referred to as Quantum Dot, QD or quantum point.) has attracted attentions as a luminescence material in recent year. For example, when excitation light is incident from a backlight to a light conversion member including the quantum dot, the quantum dot is excited to emit fluorescent light. Quantum dots having a different luminescence property can be here used to thereby emit light having a narrow half-value width, of red light, green light and blue light, realizing white light. Since fluorescent light by the quantum dots has a narrow half-value width, wavelengths can be properly selected to thereby allow the resulting white light to be designed so that the white light is high in luminance and excellent in color reproducibility. Such a technique of providing a three-wavelength light source using the quantum dots advances to thereby expand the color reproduction region from 72%, a current ratio according to TV (television) standard (FHD, NTSC (National Television System Committee)), to 100%.
The QD particle, however, is caused to have a reduced quantum yield due to oxygen, and therefore is required to be used with being protected by a barrier film. While a resin layer containing the QD particle can be protected by a barrier film to thereby allow the surface of the resin layer to be protected, a problem is that ingress of oxygen through an end portion results in deterioration of performances. In addition, there is also the following problem: light leaked from a film end portion results in a reduction in luminance.
In response to such problems, Japanese Publication of International Patent Application No. 2013-544018 discloses a quantum dot film including a barrier layer on a lateral surface of a QD phosphor material layer. And, Japanese Publication of International Patent Application No. 2010-528118 discloses performing airtight sealing to protect a composition from deterioration factors such as oxygen, water by arranging a barrier layer on the composition including a plurality of light-emitting nano crystals.